/**
 * Created by user on 2017/10/9.
 */
    public interface Stack<T> { //  Adds the specified element to the top of the stack.
         public void push(T element);
//  Removes and returns the top element from the stack.
public T pop();
//  Returns a reference to the top element of this stack //  without removing it.
public T peek();
//  Returns true if the stack contains no elements and false //  otherwise.
public boolean isEmpty();
//  Returns the number of elements in the stack.
public int size();
//  Returns a string representation of the stack.
public String toString();
    }


